Hysteresis loss and storage modulus are properties of rubber that have a significant impact on tire tread performance. Hysteresis loss can be defined by the formula tan δ=G″/G′, where G″ is a measure of the dynamic loss modulus and G′ is the measure of storage modulus, which is indicative of hardness. Generally, as the temperature of a tire increases, G′ decreases. As a result, there may be a decrease in handling.
By employing a greater amount of filler and increasing the crosslink density of the rubber, G′, as well as other mechanical properties, can be increased. These approaches, however, lead to low elasticity, higher hysteresis loss, or poor aging properties. The addition of thermoplastic polymers to rubber vulcanizates has also been proposed to alleviate G′ decreases, but the incompatibility between thermoplastics and rubber likewise can be deleterious to many of the rubber properties.
There is, therefore, a need to overcome the problems associated with the loss of G′ at elevated temperatures in tire treads.